If kasrah lacks the required inkhifāḍ and the mouth instead opens too far, the source says it can become fatḥah-like.
Practice contrasting «مِ» and «مَ». The consonant stays mīm, but the short vowel must change. Avoid opening the mouth as for fatḥah when a kasrah is written.
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Kasrah becoming fatḥah-like
Correct Vowel Articulation — Fatḥah, Kasrah, Ḍammah, Ishbāʿ and Sukūn
If kasrah lacks the required inkhifāḍ and the mouth instead opens too far, the source says it can become fatḥah-like.
Practice contrasting «مِ» and «مَ». The consonant stays mīm, but the short vowel must change. Avoid opening the mouth as for fatḥah when a kasrah is written.